Acceptable piston/bore clearance

[E30godz]

In everyones (not really) experience with building M20's and reusing stock 84mm pistons, what is an acceptable gap between the bores and pistons.

Im wanting to run some stock super e and the machine shop just told me that 5 cylinders were '2 over' and that 1 was '4 over'. I assume he means thousands of an inch.

[kenika65]

doesn't sound good to me, so I guess your building a 2.7i?

[E30godz]

correct...i guess ill be looking for a set of 85mm m20 pistons

[nando]

In everyones (not really) experience with building M20's and reusing stock 84mm pistons, what is an acceptable gap between the bores and pistons.

Im wanting to run some stock super e and the machine shop just told me that 5 cylinders were '2 over' and that 1 was '4 over'. I assume he means thousands of an inch.

I think stock is somewhere around .0020-.0025". for reference, a set of Ross forged pistons require like .008" clearance (which is why ross pistons suck). I had mine done to .0030-.0034". so yeah, 2-4 thou is pretty far out.

[digger]

stock

new 0.0004-0.0016"
wear limit 0.0047"

[nando]

oh, it's even less that I recalled.

[E30godz]

i want to be like 'come on, whats the worst that could happen' as buying pistons is going to double the projected budget...though i do hate doing things halfassedly.